The invention concerns a photoelectric scanner for use in the automatic analysis of color compositions in particular of copy masters. A scanner of this type is known for example from DE-OS-24 59 546. In the scanner described therein the scanning light coming from a light source is guided by reflection from the mirror surface of a motor-driven mirror wheel transversely to the longitudinal direction of a film to be scanned (copy master).
Another scanner is known from U.S. Pat. No. 3,677,641. In the case of the scanner described therein the copy master in the form of a film is exposed to the light of a source of light. The scanning light passes through the film and a rotating drum, in the center of which a mirror is located and having orifices in its outer wall. By the position of the mirror and the rotation of the drum orifices the detectors receiving the scanning light passing through the drum, are queried.
A further scanner is known from DE-OS-24 45 831. In the scanner described therein, the scanning light coming from a source of light impacts the copy master, for example, in the form of a film. Beyond this film a slit diaphragm is provided, which comprises a narrow slot transverse to the longitudinal direction of the film. This slit diaphragm is followed by a rotating slotted disk, the slots of which are essentially radial. If a slot on the rotating disk coincides with the slot of the slit diaphragm, a section of the scanning light is passed through and is detected by a photocell.
Scanners of this type are used for example in high capacity printers. In the case of another known scanner used in such applications a light source projects a beam of light onto a circular disk, which rotates at a short distance parallel to the copy master and contains orifices to define a point to be scanned on the copy master. The light coming from the copy master is received by a detection unit.
The trend in the scanning of copy masters tends toward higher and higher resolutions. This increasingly requires smaller and more numerous scanning points per copy master, which in turn and in different ways requires greater capacities of the detectors and of the evaluating electronics. On the one hand, the scanning time per point must be short as possible, as the number of points in the case of higher resolutions is higher, and on the other, the minimally detectable light intensity must be lower, since with identical light intensities in the scanning point but with smaller dimensions of said point, the quantity of the light impacting the detector will be correspondingly smaller. All of the aforementioned scanners have the disadvantage that the diminishing of the dimensions of the scanning point is always followed by a loss of light power. This renders the detection of the scanning light considerably more difficult.